Brake assembly



c.,A. sAwTELLE Er Ap. 1,998,096

April 16, 1935.

BRAKE AS SEMBLY Filed Aug. 25, 1939 2 Sheets-Sheet l ATTORNEYS.

April 16, 1935. c. SAWTELLE Er Ag.

BRAKE ASSEMBLY Filed Aug.

25, 1933 2 Sheets-Shea?l 2' VlNvE Patented Apr. 16, 1935 PATENT OFFICE BRAKE ASSEMBLY Charles A. Sawtelle` and Armin A. Darmstaetter,

Detroit, Mich., assignors to S. and. D. Engineering Company, Detroit, Mich., a corporation of Michigan Application August' 25, 1930', Serial No. 477,714

its Claims.

ThisV invention relates to brake assembliesv of the type having a brake band mountedfwithin a brake drum for frictional engagement with the interior surface of the brake flange and has as one of its principal objects rto provide actuating means for expanding the bandinto engagement with the brake flange so arranged with respect .to the free ends of the bandas to permit extending the said ends in close proximity'to'each'other and thereby render it possible to utilizesubstantially the entire area ofthe flange as abraking surface. By utilizing practically the entire area of the flange, maximum braking force is obtained with a brake drum of minimum diameter.A

In addition to the foregoing, the present invention contemplates a brake assembly so de'- signed as to prevent grabbing and squeaking of the brakes when applied.

Another advantageous feature of thev present invention resides in the provision of a Vbrake assembly having means associated therewith forinsuring concentricity of the brake band anddrum and also to insure substantial uniform expansion and contraction of the brake band throughout its length.

A further object of this invention resides in the provision of a brake assembly so constructed that'the wrapping force of one portioxrof the brake assists in. operating the unwrappingforce in the other portion of the brake so as to more nearly equalize. the braking efficiency of these two portions. The design of the brake assembly'is such, however, that there will always be a predominance of the wrapping force sothat the brake will be, to a certain extent, self-energ1z1ng.

A still further object of the present invention is to provide brake mechanism of the'type specified above which lends itself to economical manufacture owing to the relatively few number of parts involved'. and to the simplicity of these parts. Accordingly, other advantageous features of the .present invention reside in the novel details of construction which will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Figure 1 is a side elevational View of a brake assembly with certain parts removed for thesake (o1. 18s-Irs) onl the plane indicated by the lineA 3-3 of Figure 1;.'

Figure 4 is a'fragmentary plane View of the bra-ke band actuating arms;

Figure 5 is a detail sectional view illustrating 5 the manner in which one of the links is connected to the brake band;

Figure 6 is a sectional view taken substantially onthe plane' indicated by the line 6 6 of Figure 1; and n Figure 7 is a sectional View taken substantially ontheplan-e indicated by the line 'l-l' of Figure 1.

Generally described, the brake assembly illustrated herein comprises a brake drum I-'U ofconventionaldesign having a radially extending web portion i-i terminating at the periphery thereof in an axially extending annular brake flange I2. Positioned within then bra-ke drum Ill" concentric.

- withthe brake. flange I2 is a' suitable'bl'ake band I3' extending around; the greaterportion of the interior circumference of the flange and having the free ends operatively connected together by suitable linkage, to be presently described, for expanding and contracting the band within the drum.

. The linkage for operatively connecting the free ends of thexband comprises a pair of arms I4 and t5 extending in directions transverse to each other and arranged' in overlapping relation as shown in Figure l. The arm i4 terminates at onee'ndv in oppositely extending lateral flanges I6 conforming in curvature to the brake band I3 and adapted toV be butt-welded or otherwise' suitably secured to the free end I'I of the band to formr a continuationv thereof.l The oppositer end portion of the` arm Ill projects circumferentially of the brake band beyond the free end of the arcuate iiange- I5 and is bifurcated as at i8 for receiving the arm l5, The latter arm also terminates at the outer end thereof in a flanged portion I9 conforming in curvature Yto the brake band I3 and adapted to be butt-welded or otherwise suitably secured to the free end 2@ of the brake band to forma continuation thereof. The opposite en d portions of the arm I5 extend inwardly between 45 the furcationsV of the bifurcated portion Il of the arm I4 and extend a substantial distance beyond the free end of the flanged portion I9 thereof.

Thus, from the foregoing it will be apparent-that the fianged portions of the arms function as part of the brake band and since the arms are crossed,

as shown in Figure 1, the freefends 2| and 22 of the extensions I6 and I8, respectively, may be extended in relatively close proximity to each other with the result that substantially the entire area of the brake flange l2 is utilized as a braking surface. The advantage of the above arrangement is believed obvious since it permits obtaining maximum braking force with a brake drum of minimum diameter. lit will further be seen that the arms I4 and i5 are so positioned relative to the brake band that a force exerted upon the free ends of the arins mov-es the brake band with a combined radial and circumferential movement which results in t--e uniform engagement of the band with the brake drum throughout the length of the former.

The inner end of the arm I4 is bifurcated as at 23 for receiving the outer end of a suitable lever 24 which is pivotally connected to the fureations by means of the pin 25. The lever 24 is pivoted as at 25 intermediate the ends thereof to the plate 2i which cooperates with the web i i and brake fiange l2 to conceal the brake mechan The inner end 2S of the lever 24 is adaptto rest upon the arm 29 of a suitable bell crank lever 39 having an opposed arm 3! pivotally connected as at 32 to the free end of the arm i5. Thus, it will be seen that the arms I4 and I5 are connected together by means of the levers 24 and The bell crank lever 30 is pivotally mounted intermediate the arms upon a pin 32 between the laterally spaced plates 33 carrying the 32 and having therear ends thereof secured to the pin 25. above arrangement is such that rotation of the bell crank lever 30 in the direction of the arrow in Figure l causes the Si of the lever to actuate the end 22 of the e band, and the arm 29 to rock the lever 24 about the pin 29 in the direction of the arrow to effect an actuation of the end 2| of the brake band.

For rotating the bell crank lever 30 to effect the foregoing results, we provide a bell crank lever 34 pivotally connected by means of the pin 35 to the back plate 2l and having a relatively long arcuate arm 33 extending in close proximity to the interior surface of the brake band I3 and terminating in a lateral projection 37 adapted to extend through an arcuate slot 38 in the web I I of the drum for engagement with a suitable actuating cable 39. The shorter arm 43 of the bell crank lever 34 is provided with a cam portion 4I adapted to engage a cam surface 42 on the bell crank lever 3D. The point of engagement of the cam 4| with the bell crank lever 42 is so determined that when the arm 35 is rocked inwardly by the cable 39, the bell crank lever Will be rotated in the direction of the arrow to actuate the brake band.

As previously described, the bell crank lever 34 or the arm 35 thereof is actuated by the cable 39 which, as shown in Figure 6, is engaged within a slot 43 in the projection 31 and is provided with an enlarged head portion 44 engageable within a countersunk portion 45 of the slot and normally maintained in said engagement by the tension on the cable 39. The projection 3l is provided with a lug portion 46 exteriorly of the web Il for preventing accidental movement of the projection 3l inwardly through the slot 38. The cable 39 is guided to impart afdirect pull on the arm 38 by means of a flange 41 extending outwardly from the inner wall of the slot 38. The slot 3B is protected against the entrance of water or otherforeign elements and designed to prevent accidental displacement of the cable from engagement with the slot by means of an arcuate housing 38 secured to the web i I in any suitable manner. The above construction is such that the arm 36 of the bell crank lever 34 has sufficient travel to take up all wear of the brake band.

In order to insure the desired uniform expansion and contraction of the brake band throughout its length and to also insure concentricity of the brake band Within the drum, We provide suitable linkage 49 having the opposite ends thereof engaging the brake band at points spaced predetermined distances from the actuated ends thereof and from each other. The linkage 49 comprises a bell crank lever 50 pivotally connected by means of a pin 5I to the back plate 21 and having a relatively long arm 52 pivotally connected to one side portion of the brake band by means of a bracket 53. As shown particularly in Figure 5, the bracket 53 is provided With a portion 54 having vertically spaced openings 55 therein for receiving suitable spaced projections 56 extending from the outer end of the arm 52. As shown, the portion of the end of the arm 52 intermediate the projections 56 is substantially semi-circular for engaging the inner arcuate walls of the slots 55. Thus, it will be seen that the connection between the bell crank lever and bracket 53 is accomplished Without the use of pins or similar devices. The small arm 51 of the bell crank lever 50 is adapted to extend Within a bifurcated portion 58 of a link 59 and is pivotally connected to the furcations of the said portion by means of a pin 6U. The opposite end of the link 59 is also bifurcated and is adapted to be connected to the brake band by means of a bracket 6I extending inwardly from the latter. The inner port-ion of the bracket 6I is bifurcated as at 62 for receiving the bifurcated portion of thelink 59 and isI pivotally connected thereto by means of a pin 63 extending through the furcations of the said bifurcated portions. J ournaled upon the pin intermediate the furcations of the link 59 is an anchoring link 64 have ing the lower end journaled upon the pin 35 as clearly shown in Figure l of the drawings. In this connection it is to be noted that the opening in the bracket 6I through which the pin 63 projects is slightly larger than the pin so as to permit a slight rotative movement of the brake band and actuating means therefor, the purpose of which will be more fully hereinafter set forth.

The brake band and associated parts thereof are normally maintained in inoperative position by means of a suitable spring 65 having one end connected as at 55 to the link 59 adjacent the pivotal connection thereof to the anchoring link 64 and having the opposite end connected to the bell crank 30 at a point adjacent the connection of the arm 3l of the latter bell crank to the arm I5. The spring 65 is assisted in its function, as pointed out above, by means of a second spring 66 having the upper end connected to the bell crank lever 5S at a point spaced outwardly from the pivot 5| thereof and having the lower end connected to the free end of the arm I4. Thus, it will be seen that the spring 6G', in addition to assisting the spring 65 in returning the parts to inoperative position, also serves to yieldably maintain the inner end 28 of the lever 24 in operative engagement with the arm 29 of the bell crank lever 3|).

' Operation YWhen the parts are properly adjusted, the brake band I3 will be normally held with its braking surface slightly out of contact with the brake iiange I2and owing to the linkage 49, specified fabove,wil1 be'concentric thereto. AAssuming that theparts are inthe above position andv itis deexpandithe brake band vI3 in frictional contact Iwith the innerl surface of the brake iiange! 2 in a manner also described with someparticularity above Movement ofthe band into frictionalv engagement with the drum when the latter is rotating in the direction of the arrowl tends to rotatethe band in a corresponding direction. Limited rotation of the band in this direction is per- 'mitted owing to the slotted engagement of the 'pin-63 with the bracketl and owing to the fact that ther pin 25, constituting an anchor for the band'when rotating in the aforesaid direction, is 'free'tomove relative to the drum or in other words, functions as a floating anchor. Rotation of the band'relative to the drum develops what is 'commonly known to the trade as a wrapping "force tending to move the band into firmer engagement with the drum and the pressure built upby this force is transmitted through the arm l 4' to the anchor 25 and since this anchor is floating, there will be a tendency to move the same inwardly ofthe drum and in'so doing tend to rock the lever 24 in a direction opposite to that indicatedby the arrow .68 in Figure l. It follows,

therefore, that since the inner end of the lever 24 engages the arm '29 of the bell crank 3B, the pres sure developed by the wrapping force builds up upon the arm-29 tending to rotate the bell crank in the direction of the arrow 69 to oppose the pressure exerted upon the bell crank by the foot pedal (notshown) It will be observed, however, 'that the pressure exerted by the wrapping force tending to rotate the bell crank 3B in adirection to oppose the pedal pressure, also functions to rotate the arm 3 lof the lever 3@ in the direction of the arrow 69 and since the arm 3l is connected to the end 22 ofthe band, as shown in Figure 1, movement of the latter end in the direction of rotation of the drum willbe resisted by a force depending upon theproportion-of the levers 24 andV 30. Thus, it will be seen that the wrapping force is accurately controlled and prevented from lockingthe brake.

v'When the brake drum is rotating 'in a reverse direction as indicated by the arrowl, the band isiprevented from rotation bythe pin which is wpermanently secured to the backing plate and which is connectedto the band by the anchoring link 64 and bracket `6|. In other words, dur-I ing reverse rotation of the drum, a permanent anchor is provided for the band and the construction is such that only that portion of the band between the end 2i and the point of connection between the link 64 and band develops a wrapping force. However, since the anchor 35 is connected to the band as at 63, the pressure developed by the wrapping force is applied directly to the pin and thereby prevented from increasing the pedal pressure. The amount of wrapping force developed in reverse braking depends upon the location of the connection between the link and band which is so selected to give ideal operation. In this connection it is to be noted that in the event that the end 2| of the band moves slightly in the direction of the arrow 210, it would'not affect the pedal pressure since-.thelever-M would merely travel away.' from thebell crank. Thus, from theforegoingfitwill be observed that the pressure exerted bythelwrapping force in reverse braking'is permanently an-` chored and does notaffect'pedal pressures' with the resultthat in reverse braking only sufficient pedal pressure n'eedbe'applied to move thelportions of the band between the connectionlSSand end 22 thereof into engagement YwithltheJdruml What we claim as our invention is:

1. In-'a brake assembly, the combinationfwith a brake drum having an annular brakefflange, of a brake band mounted -withinthe drum concentricv with the flange for engagement therewith and having circumferentially spacedend portions, means vfor actuating the ends'of the lband to expand the sameagainst the 'flange'including arms'extending in oppositedirections from the ends of the Vband in overlapping relation and` having arcuate portions secured to thefree-'ends of the band formingextensions of the braking surface thereof. Y

2. In a brake assembly,-the combination-with a brake drumV having an annularbrake ange,-

of a brake band mountedwithin the drum concentric with the flange for-engagement with the inner surface thereof and having circumferentiallyspaced'end port-ions, means for actuating the ends ofthe band to vexpand the sameagainst the ange including, an arm secured to `one end of the `band and extending circumferentiallybelyond the said end, a second arm secured tothe opposite end of the band'and having a portion extending circumferentially beyond the-said end in overlapping relation'with the other" arm.

3;"In a brake assembly, the combinations/ith a brake drum having Vanannular `brake flange, of a brake'band mounted within^the drum' concentric with the flange for engagement with'the inner surface of thelatter and having circumferentially spaced end portions, means'for vactuating the end portions to expand the bandvagainst the lflange including, an arm having an arcuate'portion securedto 'one end of the band forming "an extension of the braking surface thereof and havf ing a body Yportion extending 'circumferentially beyond the op-posite endportionof'the banda second arm having .an arcuate portion secured to the opposite end of thebandito forma 'fur-v f voperatively connecting the free. ends of said arms for actuating the same. l

l4. In a brake assembly, the combination with a brake drum having an annular brake flange, of a brake band mounted within the "drum concentric with the flange for engagement with the inner surface thereof and having opposite end portions arranged in relatively close proximity to each other, means for actuating the ends aforesaid to expand the band against the Yflange includ ing, an arm secured to one end of said band and extending circumferentially beyond the same and a second arm secured to the opposite end of the band and extending beyond the latter in overlapping relation with the other arm, and means operatively connecting the free ends of said arms for actuating the same.

5. In a brake assembly, the combination with a rotating drum having an annular brake flange, of a brake band mounted within the drum con- CII centric with the flange and having circumferentially spaced end portions, a rockable lever having one end operatively connected to one of the end portions of the band, a second rockable lever having one end operatively connected to v the other end portion of the band and having the opposite end bearing upon the free end of said first-mentioned lever providing for movement of said second lever away from the first lever upon rotation of the band in one direction, and means for rocking said first-named lever in a direction to cause a corresponding rocking movement of the second lever through the bearing engagement therebetween and thereby move the end portions of the band away from each other into engagement with the drum.

6. In a brake assembly, the combination with a brake drum and a brake band associated therewith, of means permitting limited rotation of the band in the direction ofV rotation of the drum when the latter is rotating in one direction to build up a wrapping force, linkage movable with the band and operable to control the pressure developed by the wrapping force, and means for preventing rotation of the band when the drum is rotating in the opposite direction.

7. In a brake assembly, the combination with a brake drum and a brake band associated therewith, of a floating anchor for the band permitting limited rotation thereof in the direction of the drum when the latter is rotating in one direction to give a preponderance of wrapping force, means for actuating the band including floating linkage establishing a connection between the free ends of the band and proportioned to control the wrapping force, and a permanent anchor for the band functioning when the drum is rotating in the reverse direction.

8. In a brake assembly, the combination with a brake drum and a brake band associated therewith, of a floating anchor for the band permitting limited rotation thereof in the direction of the drum when the latter is rotating in one directionl to give a preponderance of wrapping force, means for accurately controlling the wrapping force including linkage establishing an operative connection between the ends of the band and movable as a unit therewith, and a permanent anchor for the band when the drum is rotating in the opposite direction positioned to give a predetermined wrapping force in this direction also.

9. In a brake assembly, the combination with a brake drum and a brake band associated therewith having actuating mechanism operatively connecting the free ends thereof and forming a unit with the same, of a permanent anchor for the band functioning when the drum is rotating in one direction to prevent rotation thereof,

and a oating anchor for the band when the drum is rotating in the opposite direction.

410. In a brake assembly, the combination with a brake drum and a brake band associated therewith, of a permanent anchor for the band when the drum is rotating in one direction selected to give a predetermined wrapping force, a floating anchor for the band functioning when the drum is rotating in the opposite direction to give a preponderance of wrapping force, and means for controlling the amount of wrapping force developed by the band during rotation of the drum in the latter direction.

1l. In a brake assembly, the combination with a brake drum having an annular brake flange, of a transversely split brake band located within the drum for engagement with the brake flange and having' laterally spaced end portions, of means permitting limited rotation of the band in the direction of rotation ofthe drum when the latter is rotating in one direction to build up a wrapping force, and means for controlling the pressure developed by the wrapping force including linkage establishing a connection between the ends aforesaid of the band and capable of restricted movement as a unit with the band.

12. In a brake assembly, the combination with a brake drum having an annular brake flange, of a transversely split brake band located within the drum having spaced end portions, of a Floating anchor for the band permitting limited rotation of the same in the direction of rotation of the drum when the latter is rotating in one direction to build up a wrapping force, and means for expanding the band into engagement with the brake flange and for also controlling the pressure developed by the wrapping force, said means including linkage connecting the free ends of the band and capable of restricted movement as a unit with the band.

13. In a brake assembly, the combination with a brake drum having an annular brake flange, of a brake band mounted within the drum concentric with the flange for engagement with the inner surface thereof and having spaced end portions, an arm secured to one of the aforesaid end portions of the band and extending beyond the said end, a second arm secured to the opposite end of the band and having a portion extending beyond the latter and in overlapping relation with ner as to provide for actuation of one ofthe V levers by the other and to permit the latter lever to move freely relative to the rst named lever. ARMIN A. DARMSTAETTER. CHAS. A. SAW'I'ELLE. 

